The present invention generally relates to polymeric printing solutions, to methods of printing polymeric printing solutions, and to articles that include one or more polyimide layers derived from the polymeric printing solution. More particularly, the present invention relates to low viscosity polymeric printing solutions, to methods of printing low viscosity polymeric printing solutions onto electronic components, and to electronic components that include one or more layers of polyimide derived from the low viscosity polymeric printing solution.
For many years, electronic components have included polymeric layers as coatings or intermediate structural films. The chemical nature of these polymeric layers and the application techniques for these polymeric layers affect the cost and properties of the electronic components. For example, the chemical nature of a particular polymeric layer may affect the thermal stability of the polymeric layer, the flexibility and durability of the polymeric layer, the ability of the polymeric layer to securely adhere to any underlying component, and the application techniques usable for the polymeric layer. Likewise, the ability to use a particular application technique for the polymeric layer may affect the application precision, the uniformity of the polymeric layer, the number of applications necessary to achieve a particular polymeric layer thickness, and the time and cost (efficiency) of polymeric layer formation.
Electronically controllable application techniques, such as ink jet application techniques, able to precisely control both application rate and location are commonly employed now when forming polymeric layers of electronic components. Such electronically controllable application techniques improve the precision and efficiency of layer formation over former techniques requiring more human labor or control.
Some types of polymeric compounds have been applied in recent years using electronically controllable application techniques. For example, some polymeric or pre-polymeric substances have been applied using electronically controllable application techniques, such as ink jet printing, to form epoxy polymer layers and acrylic polymeric layers of electronic components. Unfortunately, such epoxy and acrylic polymers are not always the most suitable choice for electronic component layers. For example, the thermal stability properties and the water absorption properties of at least some epoxy polymers and at least some acrylic polymers may not be optimum for purposes of electronic component manufacture.
High thermal stability for polymeric layers may be required during conductive material application to polymeric materials that serve an insulative function. Some epoxy polymers and some acrylic polymers that result from electronically controllable application techniques, such as ink jet printing, exhibit insufficient or less than optimum thermal stability for these conductive material applications. Also, low water absorption is desirable for electronic component manufacture to optimize operating characteristics of the electronic components. Some epoxy polymers and some acrylic polymers that result from electronically controllable application techniques, such as ink jet printing, exhibit excessive or greater than optimum water absorption characteristics for these conductive material applications.
Consequently, electronic component manufacturers have been looking beyond epoxy polymers and acrylic polymers for a polymeric material with improved thermal stability characteristics and water absorption characteristics for electronic component manufacture. Polyimide is one such polymeric material under consideration. Unfortunately, polymeric and pre-polymeric substances that yield polyimides are not entirely suitable for application via electronically controllable application techniques, such as ink jet printing. For example, the available polymeric and pre-polymeric substances that yield polyimides may be applied via electronically controllable application techniques as dilute solutions only. Due to the relatively low concentration of polyimide-yielding polymeric and pre-polymeric substances that may be using in polymeric solutions applied by electronically controllable application techniques, multiple applications are required to achieve polyimide layers of required thickness during electronic component manufacture. This unsatisfactorily diminishes the benefits of employing electronically controllable application techniques for polyimide layer formation during electronic component manufacture.
A need exists for improved polymeric substances that yield polyimides and are suitable for electronically controllable application techniques during electronic component manufacture. These polymeric substances should allow formation of polyimide layers with suitable thickness while minimizing the number of applications required by electronically controllable application techniques, such as ink jet printing, to achieve suitable polyimide layer thickness. The present invention meets these needs for improved polymeric substances that achieve suitable polyimide layer thickness with a minimum of applications by electronically controllable application techniques, such as ink jet printing.